Recently, more illumination apparatuses with a light-emitting diode chip as a light source have been developed. For example, in the field of illumination apparatuses for vehicles such as automobiles, importance is attached to low power consumption, low heat generation, the degree of freedom of design, and the like. As one apparatus that satisfies these needs, an illumination apparatus made of a light-emitting diode package including a light-emitting diode chip.
A conventional light-emitting diode package is roughly made of: a light-emitting diode chip as a light source; a lead; and an insulation structure for holding the lead. In the insulation structure, there is provided a recess portion. In this recess portion, there is arranged a light-emitting diode chip. As a result, an internal surface of this recess portion serves as a reflective surface that collects rays from the light-emitting diode chip and emits them efficiently. Incidentally, a light-emitting diode chip is smaller and hence occupies a smaller volume than a conventional bulb-shaped light source. Therefore, it is assumed to be possible to place a plurality of light-emitting diode chips in one recess portion. Therefore, with a view to improving an output of an illumination apparatus, an illumination apparatus with a plurality of light-emitting diode chip placed in one recess portion is under study.
Furthermore, aside from the above package-type one, a board-type illumination apparatus is also known. A board-type illumination apparatus is made of: a packaging substrate; a light-emitting diode chip packaged on the packaging substrate; and a reflector mounted on the packaging substrate. In the reflector, there is formed a recess portion. In this recess portion, there is arranged a light-emitting diode chip. In addition, an internal surface of the recess portion is formed into a reflective surface. Furthermore, between the packaging substrate and the reflector, there is provided an epoxy resin layer for adhesion.
Patent Document 1: Japanese Unexamined Patent Publication, First Publication No. 2005-327577
Incidentally, as a reflective surface in an illumination apparatus including the above light-emitting diode package or board type illumination apparatus, there is known a reflective surface with a shape of a paraboloid of revolution. This reflective surface made of a paraboloid of revolution has only one focus, which makes it impossible to arrange all the plurality of light-emitting diode chips at the focus. Therefore, it is typically configured such that a plurality of light-emitting diode chips are placed around the focus as a center. In the case where the illumination apparatus with such configuration is lighted, it is difficult to emit parallel rays.
Furthermore, in the recess portion provided to the insulation structure of the light-emitting diode package, there is filled a transparent resin including a phosphor. However, light rays with angles less acute than a total reflection angle defined by the ratio between the refractive index of the sealing resin and that of the air are not allowed to be emitted to the outside, leading to a problem of low light-extraction efficiency. However, if light rays are incident perpendicularly on the sealing resin, it is possible to make the light-extraction efficiency close to 100%.
On the other hand, in the aforementioned board-type illumination apparatus, a part of the rays emitted from the light-emitting diode chip is absorbed in an epoxy resin substrate layer for copper pattern insulation, leading to a problem of further lower light-extraction efficiency.
As for a parabolic reflector for multi-chips, a plurality of light-emitting diode chips are arranged in one line for optimization of the reflector shape, to thereby make it possible to maximize the generated parallel rays (for example, see Japanese Patent Application No. 2006-189206). In the case of connecting the plurality of light-emitting diode chips in parallel, each input/output lead and each of the light-emitting diode chips may be individually connected using a bonding wire. Therefore, it is possible to arrange the light-emitting diode chips in one line. However, if the light-emitting diode chips are intended to be connected in a series, it is difficult to directly connect the light-emitting diode chips using bonding wires. Therefore, it is required to provide an auxiliary lead between the light-emitting diode chips, and to connect them using the bonding wire via this auxiliary lead. This necessitates arrangement of auxiliary leads other than the input/output leads. As a result, the shape of the lead is extremely complicated. In addition, it is impossible to make a space between the light-emitting diode chips smaller. Therefore, there is a possibility that light collectivity will be decreased instead.